Lack of Toxicity in Nonhuman Primates Receiving Clinically Relevant Doses of an AAV9.U7snRNA Vector Designed to Induce DMD Exon 2 Skipping

• Published in: Human gene therapy Vol. 32; no. 17-18; p. 882
• Main Authors: Gushchina, Liubov V, Frair, Emma C, Rohan, Natalie, Bradley, Adrienne J, Simmons, Tabatha R, Chavan, Hemantkumar D, Chou, Hsin-Jung, Eggers, Michelle, Waldrop, Megan A, Wein, Nicolas, Flanigan, Kevin M
• Format: Journal Article
• Language: English
• Published: United States 01-09-2021
• Subjects: Animals; Dystrophin - genetics; Exons; Mice; Muscular Dystrophy, Duchenne - genetics; Muscular Dystrophy, Duchenne - therapy; Primates; RNA, Small Nuclear; noncoding U7snRNA; Duchenne muscular dystrophy; adeno-associated virus
• ISSN: 1557-7422
• DOI: 10.1089/hum.2020.286

Therapeutic exon skipping as a treatment for Duchenne muscular dystrophy (DMD) has largely concentrated on the delivery of antisense oligomers to treat out-of-frame exon deletions. Here we report on the preclinical development of an adeno-associated virus (AAV)-encapsidated viral vector containing four copies of the noncoding U7 small nuclear RNA (U7snRNA), each targeted to either the splice donor or the splice acceptor sites of
exon 2. We have previously shown that delivery of this vector (scAAV9.U7.ACCA) to the Dup2 mouse model results in expression of full-length dystrophin from wild-type
mRNA, as well as an internal ribosome entry site (IRES)-driven isoform translated only in the absence of exon 2 (deletion exon 2 [Del2] mRNA). Here we present the data from a rigorous dose escalation toxicity study in nonhuman primates, encompassing two doses (3 × 10
and 8 × 10
vg/kg) and two time points (3 and 6 months postinjection). No evidence for significant toxicity was seen by biochemical, histopathologic, or clinical measures, providing evidence for safety that led to initiation of a first-in-human clinical trial.